Lightweight trench box



FIG. 1 is a side elevational view of a lightweight trench box constructed in accordance with the teachings of this invention;

FIG. 2 is a top plan view of the invention;

FIG. 3 is an end view looking from the left (as viewed in FIG. 1); and

FIG. 4 is an end view of the invention looking from the right (as viewed in FIG. 1). 

The ornamental design for a lightweight trench box, as shown. 